package com.pc;


/**
 * 线程之间的通信问题：生产者和消费者问题    等待唤醒，通知唤醒
 * 线程交替执行：A,B操作同一个变量  num = 0
 * A:num+1
 * B:num-1
 * */
public class A {
    public static void main(String[] args) {
        Data data = new Data();

        new Thread(() -> {
            for (int i = 0; i < 10; i++) {
                data.increment();
            }
        }, "A").start();
        new Thread(() -> {
            for (int i = 0; i < 10; i++) {
                data.decrement();
            }
        }, "B").start();
        new Thread(() -> {
            for (int i = 0; i < 10; i++) {
                data.increment();
            }
        }, "C").start();
        new Thread(() -> {
            for (int i = 0; i < 10; i++) {
                data.decrement();
            }
        }, "D").start();
    }
}

// 等待、业务、通知
// 资源类
class Data {
    private int num = 0;

    //+1
    public synchronized void increment() {
        // 防止虚假唤醒：if => while
        while (num != 0) {
            // 等待
            try {
                this.wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        num++;
        System.out.println(Thread.currentThread().getName() + "=>" + num);
        // 通知其他线程，我+1完了
        this.notifyAll();
    }

    //-1
    public synchronized void decrement() {
        while (num == 0) {
            // 等待
            try {
                this.wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        num--;
        System.out.println(Thread.currentThread().getName() + "=>" + num);
        // 通知其他线程，我-1完了
        this.notifyAll();
    }
}
